Particulate-binder composite article and associated system and method for manufacturing the same

ABSTRACT

A system for manufacturing a particulate-binder composite article including a mold defining a mold cavity, a first opening into the mold cavity, and a second opening into the mold cavity, a mass of a particulate material received in the mold cavity, a binder source in selective fluid communication with the mold cavity by way of the first opening, the binder source including a binder material, a first filter disposed across the first opening, the first filter being permeable to the binder material and substantially impermeable to the particulate material, and a second filter disposed across the second opening, the second filter being permeable to air and substantially impermeable to the particulate material.

FIELD

This application relates to particulate-binder composites, such as metalpowder-binder composites, and more particularly, to systems and methodsfor manufacturing particulate-binder composite articles.

BACKGROUND

Rotorcraft, such as helicopters, employ rotor blades to generate lift.Specifically, rotorcraft typically include a mast that is coupled to apower plant (e.g., a jet engine and transmission assembly), and therotor blades are coupled to the mast by way of a rotor hub. Rotation ofthe mast about a mast axis causes corresponding rotation of the rotorblades about the mast axis, thereby generating lift.

In modern rotorcraft, the weight of each rotor blade is balanced toreduce vibration as the rotor blades rotate about the mast axis.Balancing of a rotor blade is commonly achieved by introducing andproperly positioning one or more tuning weights into the body of therotor blade, such as along the leading edge of the rotor blade andproximate (at or near) the outboard end of the rotor blade. Such tuningweights are formed from high-density materials. For example, tungsten iscommonly used to form such tuning weights.

Tungsten is a brittle metal with a relatively high Young's modulus.Particulate-binder composites, such as tungsten powder-bindercomposites, offer a relatively lower Young's modulus and, therefore,have been explored as alternatives to tungsten metal for use in tuningweights for rotor blades. However, traditional techniques for formingtungsten powder-binder composite articles, such as high-shear mixingunder vacuum followed by casting, are cumbersome and fail to adequatelyapproximate the density of tungsten.

Accordingly, those skilled in the art continue with research anddevelopment efforts in the field of particulate-binder composites.

SUMMARY

In one example, the disclosed system for manufacturing aparticulate-binder composite article may include a mold defining a moldcavity, a first opening into the mold cavity, and a second opening intothe mold cavity, a mass of a particulate material received in the moldcavity, a binder source in selective fluid communication with the moldcavity by way of the first opening, the binder source including a bindermaterial, a first filter disposed across the first opening, the firstfilter being permeable to the binder material and substantiallyimpermeable to the particulate material, and a second filter disposedacross the second opening, the second filter being permeable to air andsubstantially impermeable to the particulate material.

In one example, the disclosed method for manufacturing aparticulate-binder composite article may include steps of (1) placing amass of a particulate material into a mold cavity of a mold, the molddefining a first opening into the mold cavity and a second opening intothe mold cavity, (2) positioning a first filter across the firstopening, the first filter being substantially impermeable to theparticulate material, (3) positioning a second filter across the secondopening, the second filter being permeable to air and substantiallyimpermeable to the particulate material, and (4) injecting a bindermaterial into the mold cavity by way of the first opening, the firstfilter being permeable to the binder material.

In one example, the disclosed particulate-binder composite article maybe a tuning weight for a rotor blade of a rotorcraft. For example, theparticulate-binder composite article may be formed from a metalpowder-binder composite, such as a tungsten powder-binder composite.

Other examples of the disclosed particulate-binder composite article andassociated system and method for manufacturing the same will becomeapparent from the following detailed description, the accompanyingdrawings and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of one example of the disclosedsystem for manufacturing a particulate-binder composite article;

FIG. 2 is a schematic representation of the system of FIG. 1 shown withparticulate material loaded into a mold;

FIG. 3 is schematic representation of the system of FIG. 2 shown withbinder material infused into the particulate material in the mold;

FIG. 4 is a flow diagram depicting one example of the disclosed methodfor manufacturing a particulate-binder composite article;

FIG. 5 is a cross-sectional view of a rotor blade of a rotorcraftincorporating a tuning weight formed from the method of FIG. 4;

FIG. 6 is a flow diagram of an aircraft manufacturing and servicemethodology; and

FIG. 7 is a block diagram of an aircraft.

DETAILED DESCRIPTION

Disclosed are systems and methods for manufacturing a particulate-bindercomposite article, such as a metal powder-binder composite article(e.g., a tungsten powder-binder composite article). Without beinglimited to any particular theory, it is believed that the disclosedsystems and methods are capable of manufacturing particulate-bindercomposite articles having higher densities than can be achieved usingtraditional techniques because, as disclosed, the particulate materialis placed into a mold prior to binder infusion, thereby ensuring ahigher packing efficiency of the particulate material.

Referring to FIG. 1, one example of the disclosed system formanufacturing a particulate-binder composite article, generallydesignated 10, may include a mold 12, a binder source 14, a vacuumsource 16, a first filter 18 and a second filter 20. A vibrator 22 mayoptionally be vibrationally coupled with the mold 12. Additional (orfewer) components may be included in the disclosed system 10 withoutdeparting from the scope of the present disclosure.

The mold 12 of the disclosed system 10 may define a mold cavity 24having a predefined volume. In one particular construction, the mold 12may be a two-part mold that includes a first (e.g., upper) mold member12A and a second (e.g., lower) mold member 12B. The first mold member12A may be releasably connected (e.g., with a clamp, bolts or the like)to the second mold member 12B to define the mold cavity 24.Compositionally, the mold 12 may be constructed from various materials,with consideration being given to operating temperatures and pressures.

The size and shape of the mold 12, particularly the size and shape ofthe mold cavity 24, may widely vary. Those skilled in the art willappreciate that the size and shape of the mold cavity 24 may be dictatedby the desired size and shape of the articles to be manufactured by thesystem 10.

The mold 12 may define a first opening 26 and a second opening 28. Thefirst opening 26 may be formed in the first mold member 12A, and mayfunction as an inlet port. The second opening 28 may be formed in thesecond mold member 12B, and may function as an exit port. To facilitatesuch inlet/exit port functionality, the first opening 26 may begenerally opposed from the second opening 28, such as longitudinallyopposed vis-à-vis a longitudinal axis A of the mold 12.

The binder source 14 of the disclosed system 10 may be in selectivefluid communication with the mold cavity 24 by way of a supply line 30,a valve 32 and the first opening 26 in the mold 12. The binder source 14may contain a quantity of binder material 34. Therefore, when the valve32 is in an open configuration, binder material 34 may flow (see arrowF₁ in FIG. 3) from the binder source 14, through the supply line 30 and,ultimately, into the mold cavity 24 of the mold 12 by way of the firstopening 26. As one non-limiting example, the binder source 14 may be aholding tank (or other vessel), and the binder material 34 may flow fromthe binder source 14 to the mold cavity 24 under the force of gravity.As another non-limiting example, the binder source 14 may be a holdingtank (or other vessel), and the binder material 34 may move from thebinder source 14 to the mold cavity 24 by way of a pump (not shown).

The binder material 34 may be any fluid capable of flowing from thebinder source 14 to the mold cavity 24 as described herein, and whichforms a particulate-binder composite article upon contacting a suitableparticulate material 36 (FIGS. 2 and 3) and subsequent curing. Whilecertain polymeric materials are described herein, various bindermaterials 34 (including non-polymeric materials) may be used withoutdeparting from the scope of the present disclosure.

In one particular implementation, the binder material 34 may be athermosetting polymer. General examples of suitable thermosettingpolymers include, but are not limited to, epoxy resins, cyanate esters,vinylesters, polyesters, bismaleimide, polyurethanes, melamine resinsand the like. Use of other thermosetting polymers is also contemplated.

In another particular implementation, the binder material 34 may be alow viscosity thermosetting polymer. As one specific, non-limitingexample, the binder material 34 may be PRISM® EP2450, a low viscosityone-part epoxy resin commercially available from Cytec Solvay Group ofWoodland Park, N.J. As another specific, non-limiting example, thebinder material 34 may be API 1078, a low viscosity two-part epoxy resincommercially available from Applied Poleramic Inc. of Benicia, Calif.

As used herein, a “low viscosity” thermosetting polymer binder material34 may have a viscosity of at most about 100 centipoise. In oneexpression, the viscosity of the thermosetting polymer binder material34 may be at most about 90 centipoise. In another expression, theviscosity of the thermosetting polymer binder material 34 may be at mostabout 80 centipoise. In another expression, the viscosity of thethermosetting polymer binder material 34 may be at most about 70centipoise. In another expression, the viscosity of the thermosettingpolymer binder material 34 may be at most about 60 centipoise. In yetanother expression, the viscosity of the thermosetting polymer bindermaterial 34 may be at most about 50 centipoise.

The vacuum source 16 of the disclosed system 10 may be in selectivefluid communication with the mold cavity 24 by way of a supply line 38,a valve 40 and the second opening 28 in the mold 12. The vacuum source16 may be a vacuum pump, an aspirator or the like. Therefore, when thevalve 40 is in an open configuration, a vacuum may be drawn within themold cavity 24, as shown by arrow F₂ in FIG. 3.

In one alternative example, the vacuum source 16 may be omitted from thesystem 10. Rather than drawing a vacuum in the mold cavity 24 by way ofthe second opening 28, the second opening 28 may be opened to thesurrounding atmosphere (e.g., ambient air).

Referring to FIG. 2, a mass 42 of particulate material 36 may bereceived in the mold cavity 24 of the mold 12. The particulate material36 may substantially fill the volume V of the mold cavity 24.

The particulate material 36 may be various particles that, whencontacted by the binder material 34 and the binder material 34 is cured,form a particulate-binder composite article. While metallic powders aredescribed herein, various particulate material 36 (includingnon-metallic materials, such as ceramic materials and polymericmaterials) may be used without departing from the scope of the presentdisclosure.

In one particular implementation, the particulate material 36 may be ametallic powder. As one specific, non-limiting example, the particulatematerial 36 may be tungsten powder, such as tungsten powder having apurity of 99+ percent (e.g., 99.9 percent pure tungsten). Use of othermetallic powders, such as pure metal powders (e.g., lead powder; bismuthpowder) and/or metal alloy powders, as well as mixtures of differentmetallic powders, is also contemplated.

The particles of the particulate material 36 may be spheroidized. Forexample, the particulate material 36 may be spheroidized tungstenpowder. However, the shapes of the particles of the particulate material36 may vary without departing from the scope of the present disclosure.Furthermore, while the particles of the particulate material 36 may besolid, the use of hollow particles is also contemplated.

The particle size distribution of the particulate material 36 may be adesign consideration. Using finer/smaller particulate material 36 mayresult in greater particle packing efficiency and, therefore,particulate-binder composite articles with higher densities. However,finer/smaller particulate material 36 may be more difficult to handleand contain within the mold 12. In one expression, the particulatematerial 36 may have an average particle size of at most about 50microns. In another expression, the particulate material 36 may have anaverage particle size of at most about 40 microns. In anotherexpression, the particulate material 36 may have an average particlesize of at most about 30 microns. In yet another expression, theparticulate material 36 may have an average particle size ranging fromabout 15 microns to about 30 microns. For example, the particulatematerial 36 may be spheroidized tungsten powder having an averageparticle size of about 27 microns.

Referring to FIG. 2, the vibrator 22 of the disclosed system 10 may bevibrationally coupled with the mold 12. When a mass 42 of particulatematerial 36 is placed into the mold cavity 24 of the mold 12, thevibrator 22 may be actuated, thereby causing the mold 12 and particulatematerial 36 to vibrate. Without being limited to any particular theory,it is believed that vibrating the particulate material 36 prior tointroducing the binder material 34 may further improve the packingefficiency of the particulate material 36 and, thus, result inparticulate-binder composite articles with higher densities.

Still referring to FIG. 2, the first filter 18 of the disclosed system10 may be disposed across the first opening 26 in the mold 12. The firstfilter 18 may have a pore size with a magnitude sufficient to containthe particulate material 36 within the mold cavity 24 (the particulatematerial 36 generally cannot pass through the first filter 18), whileallowing the binder material 34 to pass through the first filter 18.Various filter media, such as glass microfiber filters and the like, maybe used, provided the required pore size is available.

The required pore size of the first filter 18 will depend on, amongother possible factors, the average particle size of the particulatematerial 36 and the composition of the binder material 34. For example,when the binder material 34 is a low viscosity epoxy resin (e.g., PRISM®EP2400) and the particulate material 36 is a spheroidized tungstenpowder having an average particle size of about 27 microns (e.g., OSRAMtungsten powder commercially available from OSRAM GmbH of Munich,Germany), the first filter 18 may be a glass microfiber filter having a0.7-micron pore size (e.g., WHATMAN™ 1825-047 commercially availablefrom GE Healthcare of Little Chalfont, United Kingdom). As anotherexample, the first filter 18 may be a microfiber filter having a poresize ranging from about 0.4 micron to about 1 micron.

The second filter 20 of the disclosed system 10 may be disposed acrossthe second opening 28 in the mold 12. The second filter 20 may have apore size with a magnitude sufficient to contain both the bindermaterial 34 and the particulate material 36 within the mold cavity 24(neither the binder material nor the particulate material 36 passthrough the second filter 20), while allowing air to pass through thesecond filter 20. Various filter media, such as membrane filters (e.g.,polytetrafluoroethylene membrane filter; polyethersulfone membranefilters; etc.), glass microfiber filters and the like, may be used,provided the required pore size is available.

The required pore size of the second filter 20 will depend on, amongother possible factors, the average particle size of the particulatematerial 36 and the composition of the binder material 34. For example,when the binder material 34 is a low viscosity epoxy resin (e.g., PRISM®EP2400) and the particulate material 36 is a spheroidized tungstenpowder having an average particle size of about 27 microns (e.g., OSRAMtungsten powder), the second filter 20 may be a polytetrafluoroethylenemembrane filter having a 0.2-micron pore size (e.g., WHATMAN™ 6874-2502commercially available from GE Healthcare). As another example, thesecond filter 20 may be a membrane filter having a pore size rangingfrom about 0.1 micron to about 0.5 micron.

Referring now to FIG. 3, with the mass 42 of particulate material 36received in the mold cavity 24 of the mold 12, a particulate-bindercomposite article may be formed by opening both valves 32, 40. Uponopening the valves 32, 40, a vacuum is drawn within the mold cavity 24(through the second filter 20) as the binder material 34 flows from thebinder source 14 (through the first filter 18) to the mold cavity 24.Since the first filter 18 is substantially impermeable to theparticulate material 36 and the second filter 20 is substantiallyimpermeable to both the particulate material 36 and the binder material34, the mass 42 of particulate material 36 is contained within the moldcavity 24 and becomes infused with the binder material 34. A quantity ofbinder material 34 sufficient to fill the voids within the mass 42 ofparticulate material 36 is all that is required. Once cured, theresulting particulate-binder composite article may be removed from themold 12.

Referring to FIG. 4, one example of the disclosed method formanufacturing a particulate-binder composite article, generallydesignated 50, may begin at Blocks 52, 54, 56, 58 with materialselection. At Block 52, a particulate material 36 may be selected. AtBlock 54, a binder material 34 may be selected. At Block 56, a firstfilter 18 may be selected. At Block 58, a second filter 20 may beselected. As noted herein, selection of the first filter 18 and thesecond filter 20 may include consideration of the type of particulatematerial 36 and binder material 34 selected.

At Block 60, a mass 42 of the particulate material 36 may be placed intothe mold cavity 24 of a mold 12. The mold 12 may include a first opening26 and a second opening 28, both providing access to the mold cavity 24.

At Block 62, the first filter 18 may be positioned across the firstopening 26 in the mold 12. The first filter 18 may allow the bindermaterial 34 to pass therethrough, but may be substantially impermeableto the particulate material 36.

At Block 64, the second filter 20 may be positioned across the secondopening 28 in the mold 12. The second filter 20 may allow air to passtherethrough, but may be substantially impermeable to both the bindermaterial 34 and the particulate material 36. With both the first andsecond filters 18, 20 in position, the particulate material 36 may becontained within the mold cavity 24 of the mold 12.

At Block 66, the mold 12 may be vibrated. Vibrating the mold 12, whileoptional, may improve the packing efficiency of the particulate material36 contained within the mold 12.

At Block 68, the binder material 34 may be injected into the mold cavity24 of the mold 12. Because the first and second filters 18, 20 containthe particulate material 36 within the mold 12, injection of the bindermaterial 34 fills the voids within the mass 42 of particulate material36.

At Block 70, a vacuum may be drawn within the mold cavity 24 of the mold12. While Block 70 is shown after Block 68, the step of drawing a vacuum(Block 70) may also be performed before and/or during the injecting step(Block 68). The vacuum may promote infusion of the binder material 34 bydrawing the binder material 34 into the mass 42 of particulate material36.

At Block 72, the binder material 34 may be cured. The curing technique(e.g., heat, electromagnetic radiation, or the like) will depend on thechemistry of the binder material 34. Once the binder material 34 hasbeen cured, the resulting particulate-binder composite article may beremoved from the mold 12.

Referring to FIG. 5, also disclosed is a rotor blade 80 for an aircraft,such as aircraft 102 shown in FIG. 7, which may be a rotorcraft (e.g., ahelicopter). The rotor blade 80 may include a fairing 82 that defines aninternal volume 84. Within the internal volume 84 may be a spar 86 and atuning weight 88. The tuning weight 88 may be positioned against (or inclose proximity to) the spar 86. The tuning weight 88 may be formed bythe method 50 shown in FIG. 4.

Examples of the disclosure may be described in the context of anaircraft manufacturing and service method 100, as shown in FIG. 6, andan aircraft 102, as shown in FIG. 7. During pre-production, the aircraftmanufacturing and service method 100 may include specification anddesign 104 of the aircraft 102 and material procurement 106. Duringproduction, component/subassembly manufacturing 108 and systemintegration 110 of the aircraft 102 takes place. Thereafter, theaircraft 102 may go through certification and delivery 112 in order tobe placed in service 114. While in service by a customer, the aircraft102 is scheduled for routine maintenance and service 116, which may alsoinclude modification, reconfiguration, refurbishment and the like.

Each of the processes of method 100 may be performed or carried out by asystem integrator, a third party, and/or an operator (e.g., a customer).For the purposes of this description, a system integrator may includewithout limitation any number of aircraft manufacturers and major-systemsubcontractors; a third party may include without limitation any numberof venders, subcontractors, and suppliers; and an operator may be anairline, leasing company, military entity, service organization, and soon.

As shown in FIG. 7, the aircraft 102 produced by example method 100 mayinclude an airframe 118 with a plurality of systems 120 and an interior122. Examples of the plurality of systems 120 may include one or more ofa propulsion system 124, an electrical system 126, a hydraulic system128, and an environmental system 130. Any number of other systems may beincluded.

The disclosed particulate-binder composite article and associated systemand method for manufacturing the same may be employed during any one ormore of the stages of the aircraft manufacturing and service method 100.As one example, components or subassemblies corresponding tocomponent/subassembly manufacturing 108, system integration 110, and ormaintenance and service 116 may be fabricated or manufactured using thedisclosed particulate-binder composite article and associated system andmethod for manufacturing the same. As another example, the airframe 118may be constructed using the disclosed particulate-binder compositearticle and associated system and method for manufacturing the same.Also, one or more apparatus examples, method examples, or a combinationthereof may be utilized during component/subassembly manufacturing 108and/or system integration 110, for example, by substantially expeditingassembly of or reducing the cost of an aircraft 102, such as theairframe 118 and/or the interior 122. Similarly, one or more of systemexamples, method examples, or a combination thereof may be utilizedwhile the aircraft 102 is in service, for example and withoutlimitation, to maintenance and service 116.

The disclosed particulate-binder composite article and associated systemand method for manufacturing the same is described in the context of anaircraft (e.g., a rotorcraft, such as a helicopter); however, one ofordinary skill in the art will readily recognize that the disclosedparticulate-binder composite article and associated system and methodfor manufacturing the same may be utilized for a variety ofapplications. For example, the disclosed particulate-binder compositearticle and associated system and method for manufacturing the same maybe implemented in various types of vehicle including, for example,passenger ships, automobiles, marine products (boat, motors, etc.) andthe like.

Although various examples of the disclosed particulate-binder compositearticle and associated system and method for manufacturing the same havebeen shown and described, modifications may occur to those skilled inthe art upon reading the specification. The present application includessuch modifications and is limited only by the scope of the claims.

What is claimed is:
 1. A method for manufacturing a particulate-bindercomposite article, said method comprising: placing a mass of aparticulate material into a mold cavity of a mold, said mold defining afirst opening into said mold cavity and a second opening into said moldcavity; positioning a first filter across said first opening, said firstfilter being substantially impermeable to said particulate material;positioning a second filter across said second opening, said secondfilter being permeable to air and substantially impermeable to saidparticulate material; and after said mass of said particulate materialhas been placed into said mold cavity, injecting a binder material intosaid mold cavity by way of said first opening, said first filter beingpermeable to said binder material.
 2. The method of claim 1 furthercomprising selecting a tungsten powder as said particulate material. 3.The method of claim 2 wherein selecting said tungsten powder comprisesselecting a tungsten powder comprising an average particle size of atmost about 30 microns.
 4. The method of claim 1 further comprisingselecting as said binder material a thermosetting polymer having aviscosity of at most about 100 centipoise.
 5. The method of claim 1further comprising selecting an epoxy resin as said binder material. 6.The method of claim 1 further comprising selecting as said second filtera filter that is substantially impermeable to said binder material. 7.The method of claim 1 further comprising drawing a vacuum in said moldcavity by way of said second opening.
 8. The method of claim 1 furthercomprising applying vibration to said mold prior to said step ofinjecting said binder material.
 9. The method of claim 1 furthercomprising selecting a spheroidized tungsten powder as said particulatematerial.
 10. The method of claim 1 further comprising selecting ametallic powder as said particulate material.
 11. The method of claim 10wherein selecting said metallic powder comprises selecting a metallicpowder comprising an average particle size of at most about 40 microns.12. The method of claim 10 wherein selecting said metallic powdercomprises selecting a metallic powder comprising an average particlesize between about 15 microns and about 30 microns.
 13. The method ofclaim 1 further comprising selecting as said binder material athermosetting polymer.
 14. The method of claim 1 further comprisingselecting as said binder material a thermosetting polymer having aviscosity of at most about 80 centipoise.
 15. The method of claim 1wherein said first opening is longitudinally opposed from said secondopening.
 16. The method of claim 1 further comprising, after said bindermaterial has been injected into said mold cavity, curing said bindermaterial to yield said particulate-binder composite article.
 17. Themethod of claim 16 further comprising removing said particulate-bindercomposite article from said mold after said binder material has beencured.
 18. A method for manufacturing a particulate-binder compositearticle, said method comprising: placing a mass of spheroidized tungstenpowder into a mold cavity of a mold, said mold defining a first openinginto said mold cavity and a second opening into said mold cavity, saidspheroidized tungsten powder comprising an average particle size betweenabout 15 microns and about 30 microns; positioning a first filter acrosssaid first opening, said first filter being substantially impermeable tosaid mass of spheroidized tungsten powder; positioning a second filteracross said second opening, said second filter being permeable to airand substantially impermeable to said mass of spheroidized tungstenpowder; after said mass of spheroidized tungsten powder has been placedinto said mold cavity, applying vibration to said mold; after said massof spheroidized tungsten powder has been placed into said mold cavity,injecting a thermosetting polymer into said mold cavity by way of saidfirst opening, said first filter being permeable to said thermosettingpolymer; and curing said thermosetting polymer.
 19. The method of claim18 wherein said thermosetting polymer has a viscosity of at most about100 centipoise.
 20. The method of claim 18 wherein said thermosettingpolymer comprises epoxy resin.